Shouldn't I be more empathetic?

Everyone thinks that I should be so empathetic because I live with pain on a daily basis and that I completely understand what everyone is going through when they are in pain.  Let me preface by saying that I truly don't mind listening to people complain when they don't feel well or have a legitimate complaint but please don't complain to me about a problem when it just suits you.
I know of a person who is ill, this person has every right to complain, but only complains when it suits her. She can travel for 3 hours in one day when it is something that she wants to do but when it is something that a friend asks her to do; it is just too much for her.  I just despise when people use their illnesses to benefit themselves and to use it as a crutch.  To me it is the same thing as using a handicap plate when you don't need to use it but just want a closer parking space.  I truly hope that I never get to the point where people feel that I use my illness as a crutch and if I do, please tell me.
I feel bad that I am not more empathetic towards this person but when I see her being so selfish it is so hard for me.  I truly do feel bad for her that she does have to live in pain but I just wish she would be honest with herself and everyone else and say that she just doesn't want to do it; don't blame it on an illness because one day it may become reality.